A known measuring technique within generator production lines is the so-called Partial Discharge Inception Voltage (PDIV) and Partial Discharge Extinction Voltage (PDEV) test. The test is a measure of the quality of the insulation system before shipping the generator to the customer. Over time, the quality of the insulation system deteriorates increasing the risk of breakdown.
Maintenance and repair of wind turbines is costly, in particular when the wind turbines are installed at remote places such as offshore. Further, the costs for repairing the generator insulation of the generator in a wind turbine are very low compared to replacement of the complete generator. It is therefore desired to be able to avoid catastrophic failures in wind turbine generators.